1. Field of the Invention
The present invention relates to a fluorine-containing elastomer composition, and more particularly to a fluorine-containing elastomer composition, which comprises a fluorine-containing elastomer having a cyano group as a cross-linkable group and a new type of a vulcanizing agent.
2. Related Prior Art
JP-A-59-109546 discloses a fluorine-containing elastomer composition, which comprises a terpolymer of tetrafluoroethylene, perfluoro(methyl vinyl ether) and perfluoro unsaturated nitrile compound represented by the following general formula: EQU CF.sub.2 =CF[OCF.sub.2 CF(CF.sub.3)].sub.n O(CF.sub.2).sub.m CN
where n=1 to 2; m=1 to 4, and a bis(aminophenyl) compound represented by the following general formula as a curing agent: ##STR2## wherein A is an alkylidene group having 1 to 6 carbon atoms, a perfluoroalkylidene group having 1 to 10 carbon atoms, a SO.sub.2 group, an O group, a CO group or a carbon--carbon bond directly linking with two benzene rings; X and Y each are a hydroxyl group or an amino group.
The present inventors found that a vulcanization product having good heat resistance and solvent resistance was successfully obtained by using a novel bisamidrazone represented by the following general formula as a vulcanizing agent for a fluorine-containing elastomer having a cyano group as a cross-linkable group: ##STR3## wherein R is an alkylidene group having 1 to 6 carbon atoms, preferably an isopropylidene group or a perfluoroalkylidene group having 1 to 10 carbon atoms, preferably a perfluoroisopropylidene group (Japanese Patent Application No. 6-282943).
However, as a result of further study it was found that the latter fluorine-containing elastomer composition still had a problem of processability. That is, during the preparation of a fluorine-containing elastomer composition comprising a fluorine-containing elastomer having a cyano group and the above-mentioned bisamidrazone as essential components, there sometimes happen such cases that scorching takes place or neither vulcanization products having desired physical properties nor vulcanization-molding products having a smooth surface are obtained, depending on the viscosity or the cross-linking group structure of fluorine-containing elastomer, kneading temperature, shearing spead or shearing force of roll mill or the like. When the viscosity of kneaded mixture is relatively high, a flow failure is sometimes encountered during the press molding.